High-power broad-band tunable microwave oscillator, driven by REB in plasma

Radiation spectra of plasma relativistic broad-band microwave oscillator were measured in experiments. Hollow relativistic electron beam (REB) was injected into plasma waveguide, consisting of annular plasma in a circular metal waveguide. Radiation spectra were measured by means of a calorimeter-spectrometer with large cross section in the band of 3–39 GHz. Mean frequency is tunable in the band of 20–27 GHz, spectrum width is 5–25 GHz with power level of 40–85 MW. Calculations were carried out on the base of non-linear theory, considering electromagnetic noise amplification due to REB injection into plasma waveguide. The theory predicts, that radiation regime changes from single-particle regime to collective one, if plasma density and the gap between annular plasma and REB are increased. The comparison of measurement results with non-linear theory explains some peculiarities of the measured spectrum.